Metal injection molding (MIM) is a manufacturing process in which fine metal powders may be combined with plastic binders that allow the metal be injected into a mold using standard plastic injection molding techniques. After molding and prior to removal of binders from the part, the molded part is known as a “green part”. In the traditional MIM process, binders may be used to (1) act as a lubricant so that the metal powder will flow into and fill the complex mold cavities and (2) hold the metal powders together as the green part.
Typically, about 30˜40% plastic binders are mixed with the powder before the powder is injected into the mold. After they are stripped from the molds, the green parts may be subjected to a lengthy de-binding process before sintering. The de-binding process may use a chemical solvent to dissolve and carry away most of the binder, after which the remaining binder may be baked out before sintering. Removal of the binders from the green part may result in a 30%˜40% reduction in size of the green part. Therefore, design of the parts must be meticulous since the parts may need to be fabricated 30%˜40% larger to account for shrinkage.
Therefore, a binderless metal injection molding apparatus and method may be desirable.